Bindi used the simple analogy of throwing a party and having too many guests turn up to explain her point of view.

"How is it possible that our fragile planet can sustain these masses of people?" Bindi wrote.

"Think of it this way. Pretend for a moment that I'm having a party, inviting 15 of my closest friends. I've rented a room big enough to fit 15 people, I've bought 15 sandwiches for each of my friends to eat, and I have put together 15 party bags, one for each friend.

"My party is about to start, and I hear a knock at the door. My friends are here! Only, when I open the door, 70 of my friends are standing there wanting to come to the party!

"What do I do? My room is only big enough to fit 15, with 70 we won't have any room to move and dance. I don't have enough food. Do I divide the sandwiches among the 70 people? But then everyone will still be hungry. What about the party bags? Do I only give the party bags out to my closest friends? Isn't that unfair to everyone else?

Terri Irwin, who is raising Bindi and her nine-year-old brother Robert at their Australia Zoo on the Sunshine Coast, said her daughter was less than impressed with the response from the US State Department.

"It's interesting that she was asked to write an essay about the environment and included the consideration of population (growth) and they returned her essay edited and completely edited that out," she said.

"So Bindi wrote to Hillary Clinton's organisation and said 'what happened to freedom of speech? This is my opinion and I don't want that edited out'."

The tough-talking teen – who onscreen has freed Willy, fought pirate animal poachers and hosted Bindi's Boot Camp – pulled the essay from the publication in anticipation of a response.

"The edited version was not published per Bindi's request," Mrs Irwin said.

"She said 'that's not what I wrote', so that's where we're at with it."

Secretary Clinton's department then told Bindi there was not enough time for her to do a re-write, which the Queensland teen refused to do anyway.

"Bindi just respectfully said that she's not willing to go with the edited version of the story," a zoo spokeswoman said.

"She said that while it was a good message that they were trying to convey in the publication, she just wanted her whole essay to be printed rather than just a snippet of it without the other points she wanted included.
"So that's how it's ended."

Mrs Irwin said Bindi, who is following in her father's footsteps in promoting nature conservation and helping preserve the planet, had become increasingly passionate about the cause in recent years.

"In fact Bindi is so passionate about it that she became very interested in what Dick Smith was talking about," she said.

"Dick Smith did a documentary called Population Puzzle and Bindi watched that.

"Bindi became so passionate about the issue that she talked to Dick about it and helped launch his book Population Crisis and has become a real advocate."

The mother-of-two said population growth was an unpopular topic.

"It's astounding that in just over 100 years we've gone from 1.5 billion people on the planet to 7 billion so you think 'what do we do in the next 100 years?' We're going to be warring over water and space and food," she said.

"I just think it's fascinating that when Bindi does an interview and talks about population, more than 50 per cent of the time it's edited out.

"It's something we do need to talk about or the ship's going to sink man."

Mrs Irwin said she had visited communities in Australia which were in desperate need of family planning support.

"Certainly when Bindi, Robert and I were in South Africa four years ago filming a movie we saw a lot of that in Africa as well. It's a global problem but we recognise it in Africa and we forget it's something that's in our own back yard," she said.

"Everyone talks about recycle and manage your resources but how do you do that when we've got so many people?

"It's not terribly popular but I'm not trying to insult anyone's ability to decide how many kids they want … but I continue to meet children in foster care and people living on the poverty line who did not chose to have so many children and for who options weren't made readily available."